Heat Transfer and Hydrodynamics in Stirred Tanks with Liquid-Solid Flow Studied by CFD–DEM Method

Abstract

The heat transfer and hydrodynamics of particle flows in stirred tanks are investigated numerically in this paper by using a coupled CFD–DEM method combined with a standard k-e turbulence model. Particle–fluid and particle–particle interactions, and heat transfer processes are considered in this model. The numerical method is validated by comparing the calculated results of our model to experimental results of the thermal convection of gas-particle flows in a fluidized bed published in the literature. This coupling model of computational fluid dynamics and discrete element (CFD–DEM) method, which could calculate the particle behaviors and individual particle temperature clearly, has been applied for the first time to the study of liquid-solid flows in stirred tanks with convective heat transfers. This paper reports the effect of particles on the temperature field in stirred tanks. The effects on the multiphase flow convective heat transfer of stirred tanks without and with baffles as well as various heights from the bottom are investigated. Temperature range of the multiphase flow is from 340K to 350K. The height of the blade is varied from about one-sixth to one-third of the overall height of the stirred tank. The numerical results show that decreasing the blade height and equipping baffles could enhance the heat transfer of the stirred tank. The calculated temperature field that takes into account the effects of particles are more instructive for the actual processes involving solid phases. This paper provides an effective method and is helpful for readers who have interests in the multiphase flows involving heat transfers in complex systems.

Design and Optimization of a Mixed-Flow Drying Chamber for Tiger Nuts Based on CFD-DEM Heat and Mass Transfer Model

“…This work considers the heat transfer between 'particle-particle' and 'particle-fluid'. The energy control equation for a single particle is as follows [17,[23][24][25][26][27]:…”

“…The standard k-ε turbulence model in ANSYS, the SST k-omega equation, is used as the turbulence model. The Ranz and Marshall heat transfer model and multicomponent model [15][16][17][18][19] are used because heat and mass transfer are considered in the work. In the component set, two compositions are identified: the evaporable component of water and a non-evaporable component of tiger nuts; the composition ratio is 45% and 55%, respectively.…”

“…In order to optimize the design of the drying system, the use of CFD-DEM modeling is the most effective way to achieve this goal [14][15][16][17][18][19][20]. Bin Lan et al [21] developed a CFD-DEM-IBM (immersed boundary method) method for the simulation of the particle drying process, which is useful for simulating the fluid flow, mass transfer, and heat transfer within a gas-fluidized bed.…”

Effects of Particle Suspension on Surface Vortex in Unbaffled Stirred Tanks through DEM–VOF

“…The CFD-DEM model is extensively used for simulating solid–liquid suspensions. − Sun et al developed a method coupling the volume of fluid (VOF) method with the discrete element model (DEM) based on CFD-DEM for simulating free-surface solid–liquid flow with complex wall boundaries . Our team previously developed the DEM–VOF method for turbulent free-surface solid–liquid flows in complex geometries and applied it to the study of stirred tanks. − …”

Numerical analysis and optimization of key parts in the stirred tank based on solid-liquid flow field

“…Li et al 8 carried out a simulation of an unbaffled stirred tank reactor driven by a magnetic stirring rod by Euler-Euler model coupled with the volume of fluid (VOF) method, and results showed that LES model and RNG k-epsilon model can predict the better tangential velocity and axial velocity. Luo et al 9 investigated the effects of geometrical and physical factors on light particles dispersion in stirred tank by agitation characteristic curve, and found that the agitation characteristic curves reflect the tendency of power consumption and particles distribution well in stirred tank. In addition, there are many researches 10 , 11 about simulation theory and methods of multiphase flow and corresponding case analysis.…”